Discontinuous coverage networks are radio access networks which do not provide a continuous radio coverage contrary to conventional second or third generation radio access networks as GSM or UMTS. Such discontinuous coverage networks are constituted by islands of radio coverage supporting very high bit rates and low power cells. Such networks are commonly referred as fourth generation (4G) access networks. They inter alia provide video/audio streaming services and fast downloads or uploads of large data volumes.
The islands having radio coverage are nevertheless separated by areas without any radio coverage so that applying usual handover procedures between cells according to common techniques is not possible.
In such networks, mobile terminals have a reduced mobility. They cannot leave the radio coverage area without loosing the connection.
A fast mobile IP solution is currently investigated at the IETF for solving this problem. Mobile IP solutions consist in introducing a home agent between the content server and the access controller. The IP address of the moving terminal is modified during terminal mobility. The current IP address of the moving terminal is stored at the home agent together with a permanent IP address. The mobility is totally transparent for the content server which sends the content to the permanent IP address. The translation is performed at the home agent which in turn identifies the access controller under the coverage of which the moving terminal is currently located. This solution enables it to support mobility in IP networks. Nevertheless, even if the speed of the process is accelerated, such a solution do not provide an efficient answer to the need for providing very high rate streaming services to a moving terminal leaving temporarily the zone of radio coverage.
Furthermore, if the time during which the terminal resides in an area without radio coverage is too long, the data transmission between the terminal and an external network element such as a content provider may be negatively affected in that the behaviour of an application related to the data transmission is modified. For instance, an ongoing communication could completely be stopped or a network interface might appear to be unavailable.